Understanding the interactions of the cytokines of the immune system in the regulation of the immune cascade during the host-defense mechanism is of intense scientific interest (1-2). Newly emerging research also demonstrate that some of these moleculaes act in an endocrine fashion outside the immune system (3-8). Examining these molecules as circulating endocrine communicating signals offers new scientific challenges, but this challenge has been essentially thwarted by the lack of simple, reliable assay systems to evaluate these molecules in biologic fluids of experimental animals. Although some assays exist for monitoring human cytokines, little or no attention has been focused on supporting basic cytokine research with analytical systems that evaluate murine cytokines in culture media, as well as serum. The short-term goal of this proposal is to develop an enzyme immunoassay to measure the murine cytokine, interleukin 2, however, the long-term goal is to develop a complete battery of murine cytokine enzyme immunoassays.